BC Science Probe 10Section 8.3

Organic chemistry

Organic Chemistry• Organic means living• Hydrocarbons contain hydrogen and carbon

atoms• Organic Chemistry is the study of carbon

chemicals that are natural and artificial.• The bonding in hydrocarbons is covalent so

bonding between molecules is weak.• The structure is molecular.

Percentage of Carbon

• To be considered organic, a compound must have a high percentage of carbon by mass:– To calculate the percentage of carbon, you

take the mass of carbon in the molecule divided by the mass of the whole molecule and multiply it by 100%

– If it is higher than 50%, it’s organic!

Alkanes CnH2n+2• The bond between atoms are all single.• The bonds between atoms are strong but the

bonds between molecules are weak.

CARBON CARBON

CARBON HYDROGEN

UNREACTIVE BONDS

Properties1. Good fuels: - lots of heat energy made

- COMPLETE COMBUSTION H2O + CO2

- Short chains are best (cleaner + less energy to break)

2. Do not dissolve or react with water or reactants dissolved in water: - no energy to break the unreactive C-C or C-H bonds.

Examples:

C

H

H H

H

C

H

H

HH

C

H

H

Methane CH4

Ethane C2H6

• C=C is more reactive than C-C• The molecule is unsaturated and the double

bonds allow addition polymerisation.

Alkenes CnH2n

C C

HH

HHEthene C2H4

• Functional group= OH

Alcohols CnH2n+1OH

CARBON

HYDROGEN

OXYGEN

OXYGEN

MORE REACTIVE THAN:C-C C-H

Examples:

C

H

H

H

Methanol CH3OH

Ethanol C2H5OH

O H

C

H

H

HH

O HC

H

Physical Properties1. Forces between molecules are stronger than

between alkane molecules so alcohols are liquid at room temp.

2. Alcohol molecules have a tendency to stick together because they have OH, like water but not as much.

3. Short chains mix with water.

4. Long chains are oily because more CH than OH.

Chemical Properties

1. CH part burns CO2 + H2O

2. React with Na like water but slower:OH reacts and CH is inert.sodium + ethanol sodium ethanoxide + water

• Functional group= COOH• Made by oxidising Alcohols:

1. Alcohol heated with catalyst2. Reflux condenser used to vapours are not lost but drip back into the solution.3.Organic acid collected.

• The oxidation reaction is used in breathalyser tests

• ethanoic acid (in water) H+ and ethanoate ions ions

This is reversible as the ions react and reform ethanoic acid.

Organic Acids (Carboxylic) CnH2n-1COOH

Acids

Carboxylic Acids

MineralAcids

Examples Ethanoic (Acetic) Acid,Methanoic Acid,Propanoic Acid

Hydrochloric Acid, Nitric Acid, Sulphuric Acid

Fewer H+ ions (so weaker acids and safe for use in foods etc)

Lots of H+ ionsStrong acids

Acid + Water Hydrogen ions + Other ions

HCl + H2O H+ ions + Cl- ions

REACTIVITY

AlcoholsAlkenesAlkanes

C

H

H

HH

O HC

H

C

H

H

HH

C

H

H

C C

HH

HH

EthaneC2H6

EtheneC2H4

EthanolC2H5OH

Ethanoic AcidCH3COOH

C

H

H

H

O

C

HO

EstersOrganic Acid + Alcohol Ester + Water

This is a CONDENSATION REACTION as a molecule of water is lost.

Alcohol loses OH and Acid loses H = H2O

This is HYDROLYSIS because water is used to split the ester molecules.

Sped up when heated &/or acid/alkali added

• Fruits• Plasticisers PVC• Soaps• Fats• Vegetable oils• Polyester• Laminates

MORE THAN ONE ESTER LINK

ESTER LINK

O

C

O

EsterificationEster + Alcohol Pure Ester Sample + Impurities

Esterification is this reaction when heated with some concentrated sulphuric acid to make a pure Ester.

1. Heated + reflux condenser2. Keep heating after reflux + impurities condense and out..3. Separating method: shaken alcohols, acids react with

aqueous reagents and dissolve but Ester does not.4. Calcium chloride crystals absorb moisture dry Ester5. Heat, only Ester evaporates and then condenses

PURE DRY ESTER

Fats and Oils• Fats and Oils have more than one Ester link in a

single molecule.• Fats and Oils release 5 x more energy when

oxidised than carbs. They are better energy store.

Fats Acids + AlcoholFats Fatty Acids + Glycerol (Alcohol)

O

C

O

ESTER LINK

H-C-O-C-CH2-CH2..-CH3

H-C-

H-C-

H O

H-C-O-C-CH2-CH2..-CH3

H-C-

H-C-

H O

Fats and OilsSaturated Fats Unsaturated Fats

Examples Animal Fats Vegetable Oils

State at room temp.

Solid Liquid

More H? Saturated: all single bonds, holds as much H as possible

Unsaturated: contains double bond, could take more H

Structure Straight chainRegular structure

Chains are not straightIrregular structure (does not solidify)

Health Saturated fats and trans fats are bad for you and can lead to heart disease

Unsaturated fats, omega fatty acids and CIS fats are good for you

MARGARINE:

Nickel catalyst

Vegetable oils Margarine

Unsaturated Saturated ( Heart Disease)

This is HYDROGENATIONHardening vegetable oils is cheaper than butter but it is just as harmful.

CIS Fats:Occur naturally is unsaturated fatty acids

Unsaturated2 parts of the chain on the same side of the double bond.

Trans Fats:More solid than CIS fatsStructure like saturated fatty acid Heart disease

Unsaturated2 parts of the chain on opposite sides of the double bond

Omega 3 Fatty AcidPOLYUNSATURATEFound in fishDouble bonds on every 3rd CarbonUnsaturated, good for jointsC-C-C=C-C-C=C-C-C=C

Omega 6 Fatty Acid POLYUNSATURATEFound in plant oilsDouble bonds on every 6th CarbonC-C-C-C-C-C=C-C-C-C-C-C=C

3 x Omega6 : 1x Omega3Essential part of a balanced diet